Many electronic components, such as processing units, and radio frequency (RF) devices, are commonly used in many of today's circuits and generate significant amounts of heat. For example, RF devices, such as high electron mobility transistors (HEMTs), are commonly used in radar (aircraft surveillance, weather surveillance, tactical); electronic warfare (EW), including jamming; RF communication systems; and other applications. Processing units, such as CPUs, are commonly used in computers, laptops, mobile electronics, and other applications.
A limiting factor in many of these applications is the maximum component temperature of the heat generating device, which may occur, for example, within the gate region of a HEMT. Component lifetime is a function of maximum temperature, and as such, a trade-off is often made between lifetime, maximum power output, and/or duty cycle.
The maximum component temperature in these heat generating devices is governed by heat transfer at several layers.
First, the conductive thermal resistance through the heat generating component itself is a factor in determining the maximum component temperature. The electrically active region of a heat generating device is typically located on one side of a semiconductor substrate, which may be, for example, silicon, gallium nitride, or gallium arsenide. This is the region where waste heat is generated. This heat must be conducted through the substrate before being dissipated through the thermal management system. Thermal resistance scales with thickness.
Second, the heat transfer from the surface of the semiconductor substrate to the thermal management system is a factor in determining the maximum component temperature. Thermal management systems usually conduct heat from the heat generating device into a spreader or heat sink. These systems then dissipate the heat to the ambient environment, such as via free convection, conduction, or radiation, or to a coolant, using forced convection.
Existing technologies use finned heat sinks, cold plates, microchannels, or radiators for this purpose. Thus, the heat transfer from the heat generating device can be limited by the performance of these technologies. For example, these technologies usually rely on the presence of a thermal interface material (TIM) between the component and the thermal management system. The thermal interface material, even if chosen to have low resistance, still reduces the efficiency of any solution.
Further, the size, weight, and power (SWaP) of existing thermal management solutions often drives the design of these systems and can limit their performance. For example, the system in which the heat generating device is contained may be compact, limiting the ability to transfer the heat to a cooler ambient location.
Therefore, it would be beneficial if there were a thermal management system that addressed these challenges by minimizing the conductive and convective thermal resistance in heat generating devices and reducing or eliminating the dependence on SWaP-constraining heat sinks, spreaders, and similar devices.